I have a windows dedicated server up and running. it is connected to an 8 port switch which is in turn connected to a 4 port router..

I can rcon to the server with my client machine using the internal ip for the machine the server is running on (192.168.2.102)with no problem...

However no one can rcon to the server machine from outside my home network, using either my public ip or the internal ip of the server machine..All the ports are forwarded on the router....Any thoughts??

Hmm, well..I already have the password specified in my server.cfg file..Very weird...
Anyone can join the server fine. It's just when they try to rcon changelevel de_dust for example that they have problems..."unable to connect to server" ARRGGHHH Why can they connect to the server to PLAY with no problem, but not be able to RCON????

Are you sure you have your cliesnt steam client port diffrent than the servers? that could be causing the problem. They're trying to rcon the server but its YOU they're rconing. and you have no server on your computer so they're getting an error. On your playing computer go into Steam>Play Games>COunter-Strike:Source>Properties>Launch Options in there type this: +clientport 27006

the default port is 27005 - raise it up one number. See if that helps.